The invention relates to a process for the partial combustion of finely-divided solid fuel, such as pulverized coal, in which the latter is introduced together with oxygen-containing gas via a burner into a reactor or gasifier from which a stream of high-temperature raw synthesis gas is discharged together with a minor amount of contaminating material, most of which is in the form of particles of fly ash.
Partial combustion is the reaction of all of the fuel particles with a substoichiometrical amount of oxygen, either introduced in pure form or admixed with other gases, such as a transport stream of nitrogen, whereby the fuel is partially oxidized to hydrogen and carbon monoxide. This partial combustion differs from complete combustion wherein the fuel would be completely oxidized to carbon dioxide and water.
During the process of partial combustion of pulverized coal in a gasifier, the mineral matter in the coal splits into two streams when the coal is gasified. Molten slag which is formed falls to the bottom of the gasifier where it is discharged. Lightweight particles of fly ash or fly slag which are also formed are carried out through the top of the gasifier by the stream of synthesis gas which is piped through a quench section and thence to a gas cooler, heat exchanger or waste heat boiler where steam may be generated.
The product synthesis gas and fly ash pass through equipment at high pressures, say 300 to 350 psig for example. The fly ash must then be separated from the product gas, collected, depressurized, purged of product and/or toxic gases, cooled, and converted to a form for easy disposal.